Recently, as CPUs have been driven at a higher frequency (e.g., 10 GHz or higher), attention has been focused on optical interconnection techniques which transmit signals within and between system apparatus by light. Optical semiconductor devices such as semiconductor photodetecting devices and semiconductor light-emitting devices are used in the optical interconnection techniques.
Japanese Patent Application Laid-Open Nos. HEI 2-128481, HEI 10-200200, and HEI 11-46038 disclose semiconductor light-emitting devices of so-called back emission type each comprising a substrate and a plurality of compound semiconductor layers laminated on one principal surface of the substrate, while light is emitted from the other principal surface of the substrate. For the following purposes, the part of substrate positioned under the light-emitting region is partially thinned and is surrounded by a part maintaining the thickness of the substrate. The first purpose is to prevent optical signals from deteriorating or disappearing because of optical absorption of the substrate. The second purpose is to prevent the semiconductor devices from being damaged or broken when mounted onto an external board by wire-bonding or bump-bonding.
Since the part maintaining the substrate thickness exists, however, there is a limit to the minimal size of the above-mentioned semiconductor light-emitting devices. In particular, when forming a light-emitting device array by arranging a plurality of light-emitting parts a row, the pitch between the light-emitting parts is hard to narrow, which inevitably increases the size of the light-emitting device array.